Mission work is a big part of most churches. Jesus said, in Matthew 28:19, "Therefore go and make disciples of all nations". In my opinion, mission trips do some very important things for a church.

Mission trips make you look at the larger world

Mission trips expose you to people living in very different conditions

Mission trips help to put your focus on serving other people

Mission trips often lead to a lot of soul searching and growth in your own relationship with God as you pray and prepare, and take your daily focus off yourself

Those benefits are all to the church and the people on the mission trip, but keep in mind mission trips should also help the people at your destination.  Mission trips can provide physical help and tools as well as strength and encouragement.